The non-impact, or ink jet, recording method is becoming popular as a method for converting image data in the form of electrical signals into hard copies, because less noise is produced during recording than with impact methods.
The ink jet method is considered particularly useful because ordinary paper is usable without need for a special process, such as fixing, for recording purposes as with other recording methods.
The ink jet method that has already been used comprises the steps of filling an airtight container with ink, applying a pressure pulse thereto, and emitting the ink out of the orifice of the container in a jet for recording purposes. The ink jet recorder for the aforesaid method cannot be made compact in view of its operating mechanism, and must be scanned mechanically if recording is to be made with a desired image density. This has caused the recording speed to be reduced.
Other techniques for ink jet recording have been proposed to remedy shortcomings in prior methods and to make high-speed recording possible. For example, a magnetic ink jet method has been prepared which uses magnetic ink in conjunction with a magnetic electrode array. In this method, ink-jet states corresponding to positions of picture elements have been formed by making use of swells of the ink in the presence of a magnetic field, and letting the magnetic ink jet in the presence of a static electric field. This method admits of electronic scanning and, therefore, high-speed recording becomes possible, but it is still disadvantageous in that not only the selection of ink but also coloration characteristic of the ink jet method is difficult.
There is also known the so-called plane ink jet method, which comprises arranging ink in a slitlike inkholder in parallel to an electrode array, and jetting the ink in accordance with an electric field pattern formed between an electrode facing the electrode array through recording paper. Since no minute orifice for storing ink is required in this method, failure due to ink clogging can be prevented. However, high voltage applied for jetting the ink makes it necessary to drive the electrode array on a time division basis to prevent a voltage leak across the adjoining or neighboring electrodes. Consequently, the recording speed cannot be increased to a satisfactory extent.
There has also been proposed the so-called heat bubble jet method for jetting ink out of an orifice by means of thermal energy. In this method, the ink is abruptly heated to cause film boiling and a pressure rise resulting from the rapid formation of bubbles within the orifice is utilized to jet the ink out thereof However, the film boiling temperatures are as high as 500.degree.-600.degree. C. and this makes it difficult to put the aforesaid method to practical use because the ink properties tend to change with heating and because the heating resistor protective layer provided as a heating means is deteriorated at such high temperatures.
As set forth above, there are unsolved problems associated with the ink jet methods heretofore developed, the problems including difficulty in sufficiently increasing recording speed, the necessity of employing special ink and contriving a particular driving means, and thermal deterioration of the ink and the heating means.